Sanitary tissue products often utilize fibrous structures that contain lotion and/or softening agents. Typically, such agents are designed to isolate to the surface of the sanitary tissue paper. In the case of a lotioned sanitary tissue product, surface isolation promotes the lotion transferring to the user's skin while in the case of a softened sanitary tissue product, surface isolation makes effective use of the softening agent by limiting it to a zone or zones of a the surface that are important for the perception of softness by a user.
Surface isolation is achieved by using lotions and/or softeners that have a relatively high melting point and/or contain bonding moieties which are capable of forming bonds with the fibers comprising the fibrous structure.
Formulators have found known surface isolation treatments to be lacking in providing bulk softness since they do not effectively migrate within and among fibers in order to maximally plasticize such fibers.
Accordingly, there is a need for fibrous structures that contain a bulk softening agent, sanitary tissue products comprising such fibrous structures and methods for making such fibrous structures.